As the title suggests, i'm trying to wrap my head around what differentiates an allosteric cooperativity from a chelate cooperativity by looking into this article. However i'm not able to grasp the core idea behind them.
What i understand so far, by looking in this other article, is that this two types of cooperativity give rise to the same effect at macroscopic level. The main difference is at molecular level, where in the case of chelate cooperativity the single ligands are from the same system while in allosteric cooperativity they are not.
But other than that, i'm not able to understands what this implies and why we need to differenciate between them. I would appreciate if some of you could give me some more information about this aspects and underlying their main differences.
Thanks in advance.
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$\begingroup$ You should include in questions a short summary of what you already know or found (with eventual quotes/links), so others will not write what you are already aware of, or what you should know if you searched about it. If nothing was found, write at least what (a/o where) you have searched for. This way responders avoid duplication of your effort and redundancy of internet content. $\endgroup$– PoutnikCommented Aug 19, 2023 at 13:15
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$\begingroup$ @Poutnik Hope is easer to understand now, thanks! $\endgroup$– dvdCommented Aug 19, 2023 at 13:44
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$\begingroup$ Here seems to be the free access links to your references on sci-hub.se: What is Cooperativity? and Allosteric, Chelate, and Interannular Cooperativity: A Mise au Point $\endgroup$– PoutnikCommented Aug 19, 2023 at 14:27
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$\begingroup$ @Poutnik sorry, maybe i didn't express myself well enough. I've already read the full articles when i've wrote the question, however i don't understand the difference between the two. $\endgroup$– dvdCommented Aug 19, 2023 at 15:40
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$\begingroup$ It was just a side comment for readers who do not have access to the paywalled articles. (admiting usage of sci-hub.se may be controversial). $\endgroup$– PoutnikCommented Aug 19, 2023 at 15:49
1 Answer
The cooperativity in the context of enzymes or substrates with multiple active centers is generally mutual affecting activities of these centers, by various mechanisms.
Allosteric cooperativity (AC) means the bonding of one of centers to a ligand leads to sterical reconfiguration of the enzyme, increasing or decreasing the activity (rectivity, availability) of remining centers. The typical case is hemoglobin, consisting of four enzymatic units. When one unit binds a molecule of oxygen, other units reconfigure themselves to expose their hem centers for easier oxygen bonding. This leads to steeper absorption of oxygen wit raising oxygen partial pressure, compared to a case without the AC effect.
Chelate cooperativity (CC) is typically the case when the active center is a bound atom/ion of a transition metal, intended to bound itself to a bidentate ligand, forming a chelate. In this case, after binding the first binding point of the ligand, the second bonding point of the chelate will much more probably bind as well, compared to independent ligand. another option could be two adjacent substrate active centers, binding each to one of two centers of the ligand.
In summary, CC assumes formation of chelate structure, while AC assumes reconfiguration of the structure of the substrate.
